Mesenchymal stem cells (MSCs) first found in bone marrow have a high potential as totipotent cells in regenerative medicine. MSCs may be differentiated into various types of in vivo mesoderm lineages, for example, osteocytes, chondrocytes, tendinocytes, adipocytes, myocytes, fibroblasts, and the like. Also, MSCs may be trans-differentiated into nerve cells, myocardial cells, endothelial cells, and interstitial cells under appropriate medium conditions. In addition, bone marrow MSCs express class I MHC antigens other than class II MHC antigens or express co-stimulatory molecules indicating that the MSCs have no immunogenic activities (Klyushnenkova E. et al., J Biomed Sci, 12(1): 47-57, 2005).
In addition, because MSCs exhibit immunosuppressive activities, the MSCs may be used as graft enhancers or inhibitors for fatal graft and host diseases (Le Blanc K et al., Lancet, 363 (9419): 1439-1441, 2004; El-Badri N. S et al., Exp Hematol, 26(2): 110-116, 1998).
Such MSCs may be isolated from various adult tissues such as bone marrow, adipose tissues, cord blood, peripheral blood, neonatal tissues, human placenta, and the like, but have a limitation in the number of MSCs obtained from the adult tissues.
The minimum number of cells required for cell therapy or regenerative medicine is approximately 1×109, and the value thereof further increases when cells used in experiments for establishing conditions and setting criteria are included. To supply this amount of cells from existing MSCs of various origins, the cells should be passaged at least 10 times in vitro. Then, the cells have a problem in that the cells are aged and deformed so that they are not suitable for the concept of therapy any more. This is a major drawback of the existing culture systems for MSCs to be solved. And, even when the conditions and criteria are established for using such cells, there may not be enough of the cells when the cells are used for therapy, and thus MSCs from another human origin often should be used. In this case, additional experiments should be performed for the purpose of using the other cells. Therefore, to use MSCs as a cell therapeutic agent, there is an urgent need for development of a novel method capable of increasing stemness thereof to solve the above problems.
Stemness is generally used in a related art as a meaning generally encompassing pluripotency of stem cells to produce all types of cells such as embryonic stem cells and self-renewal capacity of stem cells to unlimitedly produce self-like cells. Therefore, the stemness may include an ability of stem cells to increase telomerase activity, increase expression of stem cell-mediated factors (stemness-acting signals), increase growth of undifferentiated cells while maintaining the cells in an undifferentiated state, or increase a cell migration activity (Pittenger, M. F. et al. 1999. Multilineage Potential of Adult Human Mesenchymal Stem Cells, Science 284(5411), 143-147).
Meanwhile, endothelin (ET) is a peptide that is produced in vascular endothelial cells and consists of 21 amino acid residues, and is also known as a vasoconstrictor peptide. ET has two S—S bonds in one molecule, and is produced by modifying an ET precursor by means of an ET converting enzyme. ET-1 was first isolated from a culture broth of porcine vascular endothelial cells in 1988, and there are three types of isopeptides (ET-1, ET-2, and ET-3) in most mammals.
ET causes transient vasodilation and sustained vasoconstriction. In this case, the three types of isopeptides have substantially the same effect on the transient vasodilation, and the effect of ET-3 on the vasoconstriction action is approximately one hundredth of those of ET-1 and ET-2. An ET receptor is known to have two types of subtypes. Among these, ETA participates in the vasoconstriction action, and ETB participates in the vasodilation action.
However, it is not yet known whether ET has an effect on the stemness of human MSCs.